Approach system for landing aircraft



7 Sheets-Sheet l Jan. l5, 1952 J. B. BARTow APPROACH SYSTEM FOR LANDING AIRCRAFT Filed March 20, 1946 Jan. 15, 1952 J. B. BARTow APPROACH SYSTEM FOR LANDING AIRCRAFT Filed March 20, 1946 '7 Sheets-Sheet 2 Jan. 15, 1952 J, B, BARTQW 2,582,742

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7nn 5m M EDU mun- Bun C//Wa/:W E L @/wm s Patented Jan. 15, 1952 APPROACH SYSTEM FOR LANDING AIRCRAFT John B. Bai-tow, Blue Bell, Pa., assignor to Bartow Beacons, Inc., Philadelphia, Pa., acorporation of Pennsylvania Application March 2o, 1946, serial No. 655,702

This invention relates to systems for enabling or facilitating the landing of aircraft under adverse weather or atmospheric conditions, and

' more particularly the invention relates to a novel approach system for guiding an aircraft pilot toward a landing runway during the existence of such conditions.

'Ihe principal object of the invention is to provide an improved system which will serve to guide the pilot along a proper approach path toward the landing runway, both as regard the direction of approach and the altitude of the aircraft at any instant duringthe approach;

Experience has shown that a pair of level parallel rows of light projectors at or near ground level may be used to enable an aircraft pilot toland the aircraft under adverse weather or atmospheric conditions, provided the projectors are properly spaced and have proper light distribution to avoid glare. Thus a pair of rows of light projectors along the opposite sides of a landing` runway may be used to enable landing on the 24 clams. (climi-42.52)

runway during adverse weather conditions, as

disclosed and claimed in my prior Patent No. 2,155,295 granted April 18, 1939. If an aircraft pilot can see two properly arranged parallel rows' 1' of light sources without glare, he is able to direct the aircraft in the direction defined by such rows, and he is also able to judge the aircrafts attitude and altitude by virtue of the prospective viewing of the two rows of light sources. Therein lies the utility of two parallel rows of light sources as a means for enabling an aircraft pilot to land under adverse weather conditions. It should be noted further that it is not at all necessaryfor the aircraft pilot to see the rows of light 'sources in their entirety, as long as he sees parallel portions of the two rows at every instant during landing.

However, in order to thus utilize two rows of light sources defining the landing runway, it is necessary that the aircraft approach the runway in the proper direction and that the aircrafts attitude and altitude be approximately correct.

Ideally, the approach should be along a socalled glide path of gradually decreasing altitude toward the runway, so that when the piloted aircraft reaches the beginning of the runway, it

is not only correctly headed but has the proper attitude and altitude for landing on the runway. The present invention is concerned with the provision of adequate means for properly guiding the aircraft pilot toward the landing runway,

` even under the worst atmospheric conditions.

Heretofore, instrument approach, including radio guidance by one or more radio beacons or markers, has been relied upon to guide the aircraft pilot toward the landing runway, but such devices alone are inadequate because they are inherently incapable of guiding the pilot to the runway with sufiicient accuracy, especially'when the prevailing weather conditions are very bad as when there are changing winds or gusts or during a snowstorm. Generally speaking, instruments are not suitable for use during landing approach below safe altitudes because the pilot is not able to follow instruments closely enough, especially in view of the fact that he is bound to be under tension or strain at the time. However, instruments are useful in guiding the pilot toward the'approach area.

In accordance with the present invention, there is provided an approach system comprising controlled light sources which form an approach area including a corridor aligned with and leading to the landing runway, and which are adapted to lead the aircraft pilot into and alonglthe approach corridor. The light sources forming the approach corridor are adapted to aiord to the pilot observation of parallel rows of light sources, so that he is able to proceed alongr the approach corridor and is able to judge the altitude and attitude of the aircraft at any instant during the approach.

The present invention utilizes a principle which is described in my above-mentioned patent, i. e. that with proper spacing and light distribution a row of light sources may be made visible without glare to an aircraft pilot'traversing a path in a plane parallel to the row of light sources. In this connection, reference may be had to Figs. 8, 9, 9A and 9B of my said prior patent, and the description relative to those figv of the approach corridor.

The. invention may be fully understood by reference to the accompanying drawings in which Fig. 1 is a schematic layout or plan Lviewof an approach system according to the invention; Fig. 2 is an elevational View of the samepf Figs. 3 to 7 are explanatory illustrations;

Fig. 8 is a perspective View of a light projector unit and the associated actuating mechanism;

Fig. 9 is sectional View of the complete projector;

Fig. l vis detail view of the adjustable. linkage employed;

Figs. 1l to 13 are diagrammatic illustrations of the electrical system employed; and Y Figs. 14 and 15 illustrate the beam-adjustment indicators.

Referring first to Fig. 1, there is indicated at I- the beginning of a landing runway having par--4 allel rows of light projectors 2v on opposite, sides. thereof. The light projectors 2 may be designed and arranged in accordance with the teaching of my above-mentioned prior patentyin order that an aircraft pilot may seev the; two rows of light sources without glare as he appreaches. the runway during adverse weather conditions. As hereinbeforestated, the present invention is concerned with 1an approach system "for properly guiding the aircraft pilottoward the runway I.

In accordance'with the present invention, there isfprovided an approachsystem comprising parallel rows of light 'projectors disposed substantially at ground level and having predetermined spacing.. and light distribution, which projectors collectively form an approach area, asshown in Fig. `1. All of the light projectors are adapted ito projectlight toward an approaching aircraft,

' designated 5, '5, T..v 8, 9 and Ill, which are parallel withrthe inner rows and similarly spaced, 'so as to form Atransverse rows as Well as longitudi'n'al rows. The innermost ones of the outer rows arerclosely adjacent to the two central rows.

The lateral spacingl of the outer rows is predetermined accordingto the specific purposes of the invention as hereinafter set forth. In the specific illustration thereV are Ysix outer rows ciproj'ectors, but any desired number of such rows j maybeemployed- Theftwo'central rows of light projectors are 'adapted to project vertically-spread light beams,

while the outer'center rows of light projectors are adapted to :project horizontallyespread light beams. lIn'other words, the light beams from projectors Sand 4 are-widened or spread'out in Athe vertical sense, while the light beams from the other projectors are widened in the horizon- These characteristics of the light the small circle in each instance representing "the lightprojector and the rest of the symbol representing the stated character of the light The reason for these different beam characteristics will appear later. It should be noted V.that the symbols rin Figs. l and 2 do not represen'tlight distribution or transmission Vbutare merely intended to indicate the widening of the Ity will'be noted further that whileall. ofL the rows of light projectors commence at the beginning of the approach area (at the right end side of Fig. 1), the outer rows are of progressively shorter length, so that the approach area defined by all of the light projectors is wide at theJoegnning`v and tapers toward the landing runway I. .Stated conversely, the approach area flares outwardly toward'its beginning or starting end. This arrangement may be likened to the mouth and throat of a lfunnel or the like, andA the underlying principle of the present invention is not unlike that of a funnel in that the object. is to, direct an approaching aircraft toward. the. approach corridor.

'lreferablyL the light projectors forming the entire yapproach area are divided lengthwise of said; varea intoa plurality of banks or groups,

indicated by the dot-and-dash rectangles II,

I2 and I3, and the electrical connections supplying the light projectors are such that one or 'more 'ofj'the rbanl'csrnay be cut out if weather the. system.,

Y. spect. 'to the central approach corridor. Preferablya1l,of. the 'projectcrson one side ofl the corrider areyadapted toproject light. of one color, e.. green. while, allof the. projectors on the other side. of, the, corridor are adapted to project V "light, of. a. different color e. g. yellow. The mam .ner in, which 'thefdistinctive coloring of the light beams. -helps to. guide the .pilot toward the central, corridor will beclearly seen later.

v1 and l2, a radio beacon or marker is .represented at. I4, the same being located near the. beginning of. the 'approach area so as to .leadthef aircraft. pilot into the said area. While asingleradio. beacon is represented, a plurality' thereof `may be employed and may be arranged# asdesired.

Ideally. the approach of an aircraft such asI represented.- by the. symbol I5 in Figs. 1 and 2, should be along .an imaginary glide path I6 (FigVZ), withinl the centrally located approach corridor. However,A as- `previously indicated, a radio beacon ormarker will not suflice alone to guide, an aircraft pilot. into the approach cor-f ridor during had weatherV conditions, but can' only be reliedupon toV guide the pilot into the ap-4 proaclrareaatscme pointv along the outer boun- V(laryr thereof. There is no. assurance that the pilot will .enter the approach area centrally path so that he will be in a correct'position toland when he lreaches the landing runway I.

Referring to the previously-mentioned adjustment of the light nbeams, each of the lighty projectors in the two central rows V3 and 4 is:y 'rotatableabout a vertical axis 'through a predetermined arc so as 'to move the beams of said projectors `inwardly or outwardly. lotherlightjprojectors are rotatable about a hori-` All 0f thel zontal Vaxl's'to movethe beams thereof upwardlyv or downwardlyand these projectors are also roof travel.

tatable about a vertical axis to move their beams horizontally. The purpose of these adjustments is to adapt the system for different weather or atmospheric conditions, and to guide the aircraft pilot under different conditions in the manner presently to be described. Examplesof suitable means for adjusting the light projectors will be described hereinafter.

Generally speaking, during conditions of poor visibility, the horizontally-spread beams of the outer projectors are directed upwardly and are caused to overlap laterally of the approach area. At the same time, the vertically-spread beams of the central projectors are directed inwardly so as to make them clearly visible without glare to an aircraft pilot as he proceeds along the central approach corridor. The extent of adjustability of the light beams varies with conditions of visibility so as to insure adequate light transmission. With a given adjustment of the light beams during adverse weather conditions. an aircraft pilot entering the approach area on either side of the central approach corridor will come within the beams of some of the outer light projectors or light sources, and the color of the light will indicate to him that he is to the left or right of the central approach corridor. Hence he will direct the aircraft accordingly, and when he sees the two innermost rows of light sources each of different color, he will know that he is in the approach corridor. By reason of his continuous perspective' viewing of two or more parallel and level rows of light sources he will be able correctly to judge his altitudeand attitude as he proceeds to and thenv along the approach corridor. Thus he will be enabled to follow a proper glide pathtoward the landing runway.

The manner in which an aircraft pilot is thus guided into the central approach corridor and along a proper glide path therein may be more clearly seen with the aid of Figs. 3 to 5. Referring to Figs. 1 and 3, suppose that an aircraft pilot enters the approach area in the vicinity of the outer row of projectors '1. Fig. 3 is an elevational view in which there are represented several of these projectors which are designated 1a, 1b, 'lc and 1d. The vertical light distribution of these projectors, and their spacing lengthwise of the approach area, are such that an approaching aircraft pilot will see at least several of these light sources with substantially equal intensity and without glare, according to the principle described in my previously-mentioned prior patent. Thus in Fig. 3, let us assume' that an aircraft pilot is proceeding at some altitude or level represented by the dot-and-dash line l1. The broken lines emanating from the light sources represent'portions of the projected light beams and indicate the light distribution in a vertical direction. Since the line or path of travel l1 is at an angle to the light beam from each projector, the variation in vdistance from the aircraft to the light source substantially balances the variation in beam candle power, giving substantially uniform intensity along the path Thus the candle power of that portion cf the beam of source 'la projected to the point I3 is high, but the distance from the light source to that point is relatively great. The portions of the same beam projected to points I9, and 2| are of lesser and decreasing candle power, but the distances from the lightsourceto these points get progressively shorter. The result is that the light intensity at points I8 to 2l is .f. shortened. Therefore,

raised they are simultaneously moved inwardly substantially uniform. This eliminates any glaring or blinding eiect which wouldbe caused by non-uniformity of the light intensities at successive points along the pathof travel.

It should be noted that the intensity of light received from any of theV light sources at any point is determined by Allards law,

where I is candle power at the source, Eo is the candle power at the point of reception, D isl the unit of distance, Tis the percentage of the candle power transmitted for a given distance of atmosphere, and d is the number of units of T.

ItA should be noted also that the beams of adjacent light projectors cross one another or overlap. The high candle power portion of each beam projects into the low candle power portions of the immediately' preceding beams. Therefore, at any point along the approach path I1, the aircraft pilot will see at least several of the light sources. For example, at point IB he will see all four of the represented light sources which will appear with substantial equal intensity and without glare. A fuller explanation of the principle involved is set forth inmy above-mentioned prior patent to which reference may be had, if desired.

The purpose of shifting the light beams of Fig. 3 upwardly or downwardly, Aaccording to weather conditions and cloud ceilings, is to position the most effective portion ofveach beam to best advantage from the standpoint-of the approaching pilot. Thus when ceiling conditions are not very bad, the beams may be lowered so that they will become more eective at greater range, as the lower candle power portions of the beams. will be adequate at closer range to guide the pilot. During low ceiling conditions, the beams may be raised so that the high candle power portions thereof will be effective. In this connection, it should be borne in mind that the light transmission or penetration varies according to atmospheric conditions, and this is the reason for raising and lowering the light beams. It should be noted also that this shifting of the light beams avoids excessive brightness which might cause glare.

As previously mentioned, the horizontallyspread beams of the outer projectors are also shifted horizontally according to weather conditions. During low ceiling conditions, the visible range of these light sources is considerably when their beams are so they overlap within lthe visible range. This insures that an aircraft pilot will come within the beam spread of atleast two rows of light projectors regardless of his lateral position of approach along the outer portions of the ap` proach area. Consequently the pilot will be able to see at least two rows of light sources of distinctive color, which will indicate whether he is to the right or left of the central approach corridor. Thus the projectors of horizontallyspread light beams effectively guide the aircraft pilot into the approach corridor, giving him a true perspective to guide him.

Fig. 4 is a plan View in which there are represented several projectors of the central rows 3 and 4 of Fig. l. Thus in Fig. 4 there are four projectors designated 3a, 3b, 3c and 3d, and there are four projectors designated 4a, 4b, 4c and 4d. The central vertical plane of approach in the 'to the time, i. e. day or night.

direction of the arrow isrepresented bythe-'dotand-dash'linef'ZZ. .The broken linesrepresent lightfrom the several sources to some point 23 in plane 22. Fig. is a transverseelevational view wherein sources v3b and ib are shown. in accordance with the principal of the aforementioned prior patent, thelight distribution of the two rows of projectors is such that a plurality of these light Vsources are visible to the pilot with substantially equal intensity at any point in the `vertical-plane'22. l Thus, when the pilot has entered Vthe approach corridor, he is enabledto travel along a proper descending path toward the "runway, due to his perspective viewing of the corridor-forming light sources without glare.

The reason for shifting the beams of these projectors inwardly and outwardly accordingto weather conditions, as hereinbefore mentioned, is thesame as described in connection' with the raising and lowering of the outer-beams, i. e. to

position the high 'and low candle power portions of the beams to best advantage. Thus when the weather conditions are not very bad and with good light transmission, the central beams are shifted outwardly making them visible from longer range, since the low candle power portions ofthe beams are suiiicient at close range Vto make the light sources visible without glare to guide the pilot along the approach corridor. However, when weather conditions are very with-low' light transmission, the said beams are corridor, he is able to judge the aircrafts altitude and attitude and is thus able to move along a proper approach path until he reaches the landing runway. Y

rThe shifting lof the diiferent light beams is eiected according to the ceiling and ground visibility at anyV particular time, and also according Since the outer light beams serve to guide the aircraft pilot into the'approach corridor while he is at a safe altitude, the shifting of these light beamsY is effected .according to the existing ceiling. On the other hand, since the central beams forming the approach'corridor serve to guide the aircraft pilot during Va downward glide preparatory to landing, the shifting of these light beams lis efected according to the existingv ground visibility;

`By""ground visibility is meant the visibility, or

transmission ofthe atmosphere, under the vcloud base which is referredto as the ceilingL When the ceiling is low or'zero, the hori'zontally-spread light beams are raised to or near their maximum inclination lto the 'ground'and are moved inwardly toward the approach corridor. When the ceiling is relatively high, these beams are lowered and are moved outwardly.

When the ground visibility is poen-the' centrally` located vertically-spread beams are idirected inwardly, and Awhen the ground visibility is relatively good, these beams are moved outwardly.

V Figs. 6 and ,'7 represent beam adjustments of a transverse rowV of light projectors for extreme conditionsV of ceiling-and ground visibility. Fig. 6 represents the beam positionsv for high' ceiling and good ground visibility, while Fig. 7 represents lthe 'beampositions'for lowl ceiling and .poor

ground' -vv'isilzility.v Since the .corridor-forming projectors'and the outer projectors are adjustable independently', as hereinafter described, they can `be adjusted for any conditions, such as low .ceiling with goodground visibility or high ceiling with poor ground visibility.

Referring now to Figs. 8 to 10, there is illustrated one form of a mechanism which may be employed to adjust vthe light projecto-rs in accordance with the foregoing description. The sametype of mechanismv may be employed to actuate the innermost and outer projectors, as

the mechanism Vis adjustable to provide the different adjustments of the horizontally-spread and vertically-spread light beams. Therefore it is only necessary to illustrate a single mechanism, it being understood that the same type of mechanism is employed for each of the light projectors in the entire system.

As shown in Figs. 8 and 9, the light projecting unit 24 is removably mounted on a support 25 by means of suitable clasps 25. The support 25 is pivotally carried by a yoke 2l for movement Aabout a horizontal axis. To this end the arms of yoke 2l' extendvertically adjacent the support 25, and the yoke carries horizontal pivot pins 28 upon which the support'25 is mounted. The yoke' 21, inl turn, is mounted for rotation about a central vertical axis. A horizontal supporting panel or plate 29 carries a bearing support 35i, andthe yoke 2l has a centrally located depending rod or'shaft 3l whichseats in the bearing support 3B.

A reversiblemotor 32 is also mounted on the supporting .panel 29, andits armature or rotor is mechanically coupled to a screw shaft 33 which is'rotatably supported by bearings 34 and 35 mounted on supporting blocks 36 and 31. The latter alsosupport a. plate 38 which extends below the screw shaft 33 in parallel relation therewith. A nut 3^9 threadedly Vengages the screw shaft and is supported thereby. It Vwill be noted that the nut slides'along the plate 33 as the screw shaft rotates. An arm 4u extends between yoke 21 -f and nut 39. One end of arm 4i? is slotted at 4;!

and seats in a central recess of yoke 21, being held by screw V42. The other end of arm it carries a pin '43 which rides in a recess 43a of nut 39. t will be obvious that the light projector unitA 2d may be caused to rotate in either direction about itsv central vertical axis of rotation by operating the reversible motor 32 in either direction, and the rate of movement may be varied by means ofthe adjustability aiorded by slot 4l and screw 42. vTauch adjustability enables different rates of movement of the inner and outer projectors, and it 'also enables different rates of movement of the rows of outer projectors. Thus, it may be desired to have the outermost rows of projectors move faster than the other projectors. Y

To effect'rotation of the light projector unit 24 about its horizontal axis Vof rotation there is provided a linkage .device nowv to be described.

-A sleeve 44, mounted on top of motor 32, ad-

justably carries .a rod 45 which extends above the screw shaft33 .and parallel therewith. A set screw -46 enables longitudinal adjustment of the rod 45. This rod is bent laterally at its end l4'1 and is connected to a link 48 by means of a .the lower pai-t ef support 2-5. Tothis end. the

astenia 9' stud 50 has an integral shank l53' which isV threaded at its end to receive a wing nut 54.

It will be noted that the slot 52 is so locatedA and is of such length that the stud 50 may be centrally positioned in alignment'with the vertical rotational axis of the light projector unit 24, or it may be adjusted to some point off center. When the stud is centrally positioned, the linkage has no eiect on the light projector unit 24 and the latter simply rotates about its vertical axis as the screw shaft 33 rotates. However, when stud 50 is adjusted to a position Iother than its central position, vthe linkage causes the light projector unit 24 to rotate about its horizontal axis at the same time that it rotates about its vertical axis. By virtue of the ladjustability of rod 45 and stud 5U, itis possiblev to effect different amounts of rotation of unit 24 about its horizontal axis for a given amount of rotation of the unit about its vertical axis.

As stated above, each of thelight-projecting devices employed in the approach system provided by the present invention may be of the form illustrated in Figs. 8 to 10. Each device of the two-innermost rows shown in Fig. 1 may have the stud 58 adjusted to the central position so that the light projectors will move only in the horizontal sense to move the verticallyspread beams inwardly and outwardly, as above described. The outer devices, however, will have the stud 58 adjusted to an offset position so that these projectors will be moved in both the vertical and horizontal sense to move the horizontally-spread beams in the manner above described. Obviously, the utilization of a single form of mechanism which is adaptable for the inner and outer light 'projectors is highly desirable from the standp-ointtof simplicity and uniformity. It should be noted 'that the removability of the light projector unit 24 enables the insertion of different types of units adapted respectively to project horizontally and vertically spread light beams. O-f course, the character of the beam and the light distribution are dependent on the lens of the unit. l

Each light projector and its associated operating mechanism may be encased in a moistureproof transparent housing, as shown in Fig. 9.l The housing may comprise a base 55 and a transparent dome 56. The base 55 may be shaped as illustrated and may be provided with lugs 51 to seat the supporting panel 29. A seal may be effected between the dome and the base by means of a resilient sealing ring 58. The dome may be held in place by means of suitable latch devices, one of which is shown at 59. The entire unit may be placed on'the ground, which is represented at 68, or it may be mounted on a support, such as a post, so as to be above the ground.

To provide the desired coloring of the light beams, as hereinbefore mentioned, a color screen may be provided in each projector. Preferably a dome-shaped color screen 6| is provided, having two half sections 62 and 63, one adapted to provide green or yellow and the other adapted to provide red. If it is desired to prevent landing of aircraft on a particular runway, the color screens of the various projectors may be rotated through 180 to produce all red light beams. To this end, each projector is provided with a motor 64, and all of the motors may beactuated simultaneously. Y The color screen 6i is carried by Va. ring 65 whichv rests on rollers 66 carried by base member 55'." Ring 65has gear teeth formed thereon which mesh with a pinion 68 driven by the motor 64. The latter is mounted on a bracket 69 secured to base 55.

For simplicity of illustration, the supply conductors for the lamp and motors are not shown in Fig. 9. Such conductors may be brought into the housing at the bottom thereof. y

In Figs. 11 to 13, there is diagrammatically illustrated an electrical system or arrangement which may be employed. Fig. 11 illustrates certain apparatus which may be located in a control tower. Fig. l2 illustrates other apparatus which may be located in a control vault. Fig. 13 illustrates diagrammatically the electrical connections tc the light projecting devices of an approach system. In considering these illustrations, it is to be understood that the correspondingly designated terminals are intended to be connected together.

A complete aircraft landing field might comprise four runways extending radially from a common juncture at right angles to one another. In the control tower there may be provided a miniature replica of the complete landing field, as represented at 10 in Fig. 11. At the central portion 1| of this replica the four runways are shown and veach has an associated approach system. The four sections of the-simulated landing fields are designated No. I, No. 2, No. 3 and No. 4. Each of the four approach systems has three sections corresponding to those in Fig. 1 and designated by the letters R, S and T.

The replica 10 serves as an indicating means to indicate the light projectors in operation Vat any particular time. To this end, the replica 10 may be in the form of an opaque board or chart having openings or transparent areas representing the various light projectors, as indicated by the d ots 12. Suitable lamps may be kdisposed behind the various sections of the chart to indicate operation of a particular group of light projectors. In the illustration, lamps 13, ,14 and 15 are represented in association with the respective sections R, S and T of each approach system. Of course it will be understood that more than one lamp may be associated with each section. lIi" necessary, suitable light shields or barriers may be employed to confine the light of each lamp to itsparticular section.

The indicating lamps are controlled by selector switches 16, 11 and 18 each of which has'four positions. Switch 16 controls lamps 13 over conductors 18; switch 11 controls lamps 14 over conductors and switch 18 controls lamps 15 over conductors 8|. The three switches are preferably ganged for operation by a single control. By means of these switches, any one of the four runways and its associated approach system may be selected, and a corresponding indication will be given on the replica chart 18. To this end, the stationary contacts of the said switches are connected to certain apparatus in the control vault and in the eld by Way of terminals designated by the letters R, S and T with numeral subscripts. The connections will be described later.

In addition to the above-mentioned switches, there are provided control switches 82, 83 and 84, by means of which the three sections R, S and T of each approach system may be controlled. It

' will be noted that the switches 82, 83 and 84 are connected Aso that when all three of them are closed, all of the light projectors of an approach system are energized. When switch 84 is opened, the projectors of the outer section T are de-energzed. Similarly,`the switch 83 controls the inter- 1-.waia-teV section s, an@ the switch a2 commis the brightness .or light intensity of the operating light projectors, according to atmospheric conditions. A switch `B9 servestsincrease or decreasek the brightness, this switch being. eormetel 'G0 appara'. tus in the control vault b y wayof terminals A and B-V A brightness indicator 90 Ais also C011- nected to the apparatus in the control vault by way of terminals D and E.

A common return conductor 9| connected to one side of the supply line 92, and the various indicator lamp circuits and Vother `connections are completed by Way of this conductor, as indicated by the terminal designationgC.

Referring now to Fig, 12,. the light projectors of the alcoroechsystem are eesreiedfrom a Suitable s'ource connectedto terminals 9?Y and an associated transformer 94., The desired voltage is derived by wayof conductors- 95 andwhich are connected to, the. various .light projectors by way of terminals U and V. A .second transformer 91|` supplies a suitable Voltage to the brightness indicators 90 and 9 8. The brightness or light intensity is controlledby means, of avariable tap 99v on the secondary winding of transformer 95, which tap is actuated by a screwshaft driven byA areversible motorcll. It will be noted that f motor 0| maybe voperated in either direction by means of switch 89 shownin Fig. 1l.

Switches '85 and 86, previously mentioned, confy trolthe energization of relays |02, |03, |04 and |05. A three-.phasesupplyline |06 is preferably employed to energizethe-motors associated withv the various light projectorslffor moving the light beams vas Vpreviously described. The motors may be single phase motors of modern design. The relays |02 to |05 effect reverse operation of the beam-shifting. motors, under control of switches 85 and 86, by interchanging the connections of the three-phase supply line. The relays |02 and |03, which are controlledV by switch 85, control the supply of current via conductors |01 to the motors associated with the corridor-forming light projectors whose beams are verticallyA spread, while, relays |04 and |05which are controlled by switch 86, -control the supply of current Via conductors |08 to the outer light projectors whose beams `are horizontally spread. V

Extending from conductors |01 and |08 are four groups of conductors |09, ||0, and 2 which are connected to the beam-shifting motors of the; four approach systems. .The relays H3, H4, ||5u and |,I64se1ect any desired one of the said conductor groups according to the position of switch 1E.Y All of the motorscof the selected approach system are operable by switches 85 and 86 as long as switch 8 2 is closed, regardless of whetherthe projector lamps are energized;

Referring now to Fig. 13, there is shown a single approach system and its associated runway corresponding to the system shown Fig. 1. As in Fig. 1 the runway is designated' whilel the severalsectons ofthe approach systemaredesisge nated ll. l2 and I3.Y respectively. The lightingV current for all ofthe light Vprojectorsof the approach system shown is vsupplied by way of con: ductorsf ||1. -Thebranchfcircuits |I8, H9 and |29 leading to the vdiiferent sectionsof the approach system are controlled by relays |2|, |22 and |23. These relaysare controlled by means of the switches 82. 83 s114184. respectively, of Fis. 11. Assumingthatthe approach system shown in Fig. 1 3,i s thatdesignated No. 2in Fig. 11, the windings of relays |2|, V|22 and |23l will be oo n-` nected to the terminals R2, Saand T2 in Fig. ll.

In Fig. 13, there are. twothree-conductor ca,- bles .I 214 and.v |25. the conductors of which are. connected to conductors H0 of Fis. 12. Cable |24supplies currentv from conductors 91 (Fig. 12,) to the beam-shifting motors of the. corridorforming projectors of the approach system shown in Fig. 13, Cable |25 supplies current from conductors |08 to the beamshifting motors of the Outer projectors of .the approach'system shownrin Fig, 13. f

For .simplicity of illustration, the electrical .connections to the various projectors in Fig. 13 are represented by single lines.

The other three approach systems (not shown) may be similar tothat of Fig. 13, the motorfsupfply conductors being connected to the conductor groups |08, and ||2 o f Fig. 12.

Since the colorechanging arrangement previ ously described isvoptional the electrical connec tions for supplying ythe color-changing motors' have not been shown in Figs., l1 to 13. It suffices. to state that such motors, Vif employed, may be, supplied and controlled in the same way that the beam-shifting kmotors are supplied and con-v trolled. In such case, pr ovi sion may be'made to indicate in the controltower the color of the projected light. Thus the indicator board may have red lights whichV are energized when the projectors are caused to emit red light.

The horizontal and vertical adjustment indicators, previously mentioned, may take the form shown in Figs. 14 =and 15. The horizontal indicator, which shows adjustment of the verticallyspread beams, mayy comprise a calibrated and marked dial |26 anda motor-driven pointer |21; and similarly the Vertical indicator, which shows adjustment of the horizontally-spread beams, may comprise a calibrated and marked dial |23 and a motor-driven-pointer |29. TheV dial |26 (Fig. 14) may have two scales indicating dayV and night ground visibilities in feet and miles, while the dial |28 may have two scales indicating ceiling in feet. The switches 8 5 and 8E may be associated with-'the indicators as illustrated,

While the invention has been described with reference to the embodiment illustrated, it will be understood that various modifications are pos--` sible and the invention is not limited to the particular embodiment shown and described.

- 1. Anapproach system for guiding an aircraft pilotl toward'a landing runway during landing of the aircraft especially under j adverse weather conditions, comprising a plurality of rowsof light projectors arranged to form an approach corridor aligned with and leading to said runway, said projectors being adaptedtoproject horizontally nar.- row and vertically widelight beams, and other rows yoij light projectors parallel tothe corridorforming rows .on theA oppositesides of thecorridor and iormins therewith, an approach. aree., saldf other projectors being adapted to project vertically narrow and horizontally wide light beams.

2. An approach system for guiding an aircraft pilot toward a landing runway during landing of the aircraft especially under adverse weather conditions, comprising a plurality of rows of light projectors arranged to form an approach corridor aligned with and leading to said runway, said projectors being adapted to project horizontally narrow and vertically wide light beams, other rows of light projectors parallel to the corridorforming rows on the opposite sides of the corridor and forming therewith an approach area,

said other projectors being adapted to project vertically narrow and horizontally wide light beams, and means for moving the various light projectors so as to shift the light beams according to different weather conditions.

3. An approach system for guiding an aircraft pilot toward a landing runway during landing of the aircraft especially under adverse weather conditions, comprising a plurality of rows of light projectors arranged to form an approach corridor aligned with and leading to said runway, said projectors being adapted to project vertically' spread light beams, other rows of light projectors parallel to the corridor-forming rows on the opposite sides of the corridor and forming therewith an approach area, said other projectors being adapted to project horizontally-spread light beams, and means for moving the various light projectors so as to shift said vertically-spread light beams horizontally and to shift said horizontally-spread light beams both vertically andy horizontally, whereby to adapt the system to different weather conditions.

4. An approach system for guiding an aircraft pilot toward -a landing runaway during landing of the aircraft especially under adverse Weather conditions, comprising a plurality of rows of light projectors arranged to form an approach corridor aligned with and leading to said runaway, said projectors being adapted to project vertically-spread light beams, other rows of light projectors parallel to the corridor-forming rows on the opposite sides of the corridor and forming therewith an approach area, said other projectors being adapted to project horizontallyspread lightbeams, the approach area comprising a plurality of sections longitudinally, means for selectively energizing the lamps of the light projectors according to said sections, each of the light projectors including a motor and mechanism for shifting the light vbeams according to different weather conditions, the verticallyspread light beams of the corridor-forming projectors being shiftable horizontally and the horizontally-spread light beams of the other projectors being shiftable both vertically and horizontally, means operable at will to energize the motors of the corridor-forming projectors, and other means operable at will to energize the motors of the other projectors.

5. An approach system for guiding an aircraft pilot toward a landing runway during landing of the aircraft especially under adverse weather conditions, comprising a pair of rows of light projectors arranged to form an approach corridor aligned with and leading to said runway,-

said projectors being adapted to project verticallyspread light beams, and having such spacing and such light distribution that a plurality of the projectors of each row are visible with sub-v. stantially equal intensity from any point in avertical plane midway between said rows. and

llt outer 'rows of light projectors `parallel to the corridor-forming rows on the opposite sides of the corridor and adapted to lead the pilot into said corridor, said outer projectors being adapted to project horizontally-spread light beams which overlap to form an approach area, the light projectors of each outer row having such spacing andV such vertical distribution of light that a plurality of said projectors are visible to a pilot approaching at a certain altitude with substantially equal intensity.

6". An approach system as defined in claim 5, wherein the projectors are adapted to give a color indication of the pilots position with respect to the approach corridor.

7. An approach system for guiding an aircraft pilot toward a landing runway during landing of the aircraft especially under adverse weather conditions, comprising a pair of rows of light projectors arranged to form an approach corridor aligned with and leading to said runway, said projectors being adapted to project vertically-spread light beams, and having such spacing and such light distribution that a plurality of the projectors of each row are visible with substantially equal intensity from any point in a vertical plane midway between said rows, outer rows of light projectors parallel to the corridorforming rows on the opposite sides of the corridor and adapted to lead the pilot into said corridor, said outer projectors being adapted to project horizontally-spread light beams which overlap to form an approach area, the light projectors of'each outer row having such spacing and such vertical distribution of light that a plurality of said projectors are visible to a pilot approachingat a certain altitude with substantially equal intensity, means for adjusting said corridor-forming projectors to adjust their beams according to ground visibility, and means for adjusting said outer projectors to adjust their beams according to ceiling.

8. An approach system for guiding an aircraft pilot toward a landing runway during landing of the aircraft especially under adverse weather conditions, comprising a plurality of rows of light projectors arranged to form an approach corridor aligned with and leading to said runway, said lprojectors being adapted to project horizontally narrow and vertically wide light beams, other rows of light projectors parallel to the corridor-forming rows on the opposite sides? of the corridor and forming therewith an approach' area, said other projectors being adapted to project vertically narrow and horizontally wide light beams, the approach area comprising a plurality of sections longitudinally,

and meansv for selectively energizing the lamps of the light projectors according to said sections.

spread light beams, each of the light projectors including a motor and mechanism for. shifting the light beams according to different weather conditions,- the vertically-spread light beams of the 1 corridor-arming projectors teilig shifted@ projectors being adapted to :project v'horizontally narrow and 'vertically wide .light beams, outer rowsrofflight projectors apara'llel to thencorridor forming rows on the vopposite :sides pf ithecorridor and adapted to lead thefpilotintofsaidacor-f. ridor, said'outer projectors :being .fadaptedto project vertically narrow :and horizontally v.wide light beams which 'overlap to :form approach zarea, means .for positiona'lly adjusting :said :corridorforming .projectors to :shifttheir beams according lto :ground `visibility .and means 'for positionally adjusting said ,outer projectors to shift @their beams according to ceiling. u Y

.1 l. An approachrsystem :for guiding an 4aircraft pilot toward a .landing runway .during land-ingof the aircraft vespecially under :adverse :weather conditions, comprising 'a pluralitylof .rows of light projectors arranged to :form 2an approach cor ridor Valigned with `and leading yto :said runway,

said projectors being adapted to project vhorizontally narrow and vertically wide light beams, other rows of vlight projectors :parallel toV .the

corridor-.forming .rows Aon the yopposite sides 'ciV the corridor and forming therewith an :approach area, vsaid .other proj ectors Ybeing adapted to .project vertically narrow and horizontally wide light beams, and means for controlling the intensity of Ythe light beams according to l.difiere-:nt avea-ther conditions.

l2. An' approach system fiorguiding :an :agircraft'pilot toward a landingrunway during land.- ing of the aircraft especially under v:ad-verse weather conditions, comprising -a plurality =of rows of lightfproj'ectorsarranged :to fform .anfallproach corridor aligned with and leadin'gto said runway, said projectors 'being nadapted'to project horizontally narrowxand vertically wide ,light beams, other rows yof .light 'projectors parallel to the corridorefcrming rows on 4theopposite sides of .the corridor and :forming therewith an approach area, said other projectorsbeing adapted to project vertically narrow and horizontally wide light beams, means for moving the z'various light projectors so as to 'shift .their :light :beams according to different weather conditions, .and means for controlling vthe intensity :of the 'light beams according to said conditions.

13. An approach system Ifor :guiding yanraircrialft corridor and Yadapted to lead'the pilot vinto said corridor, said Vouter projectors being vadapted to project horizontally-spread light .beams which overlap to .form 'an approach area, the 'light'pro-L jectors rof each outer row having such vspacing and such vertical distribution of light thataplurality of said projectors are visible to a pilot ap proaching at a certain altitude with substantially equal intensity, and means for moving the Varions light projectors so as to shift said verticallyspread light beams horizontally and torshift said horizontally-spread light beams both 'vertically and horizontally,whereby to Yadapt the system to different weather conditions.

14. An vapproach system Afor guiding an raircraft pilot toward a landing .runway .during .land ing 'of the aircraft especially under adverse weather conditions, comprising .a pair of .rows oi light projectors arranged 'to form an approach corridor valigned with and leading to vsaid runway, said projectors being adapted to project vertically-spread light beams, and .having :such spacing and such light distribution that a plurality of the projectorsof each row are visible Y with substantially equal intensity from any point Y in a vertical plane midway between said rows,

pilot toward a landing'runway .during landing 'of the aircraft especially Aunder .adverse weather conditions, comprising a pair iof 'rows fof .light projectors arranged `to form fan approach corrider-#forming l-ro'irzs -on .the opposite .sides of theouter rows of light projectors parallel to the corridor-forming rows on the opposite sides of the corridor and adapted to lead the pilot into j saidcorridor, said outer projectors being adapted to project horizontally-spread light beams which overlap to form an approach area, the light projectors of each outer row having such spacing and such vertical distribution of light that a plurality of said projectors are visible Yto a pilot approaching at a certain altitude with substantially equal intensity, :each of `the 'light projectors including a motor and mecha-nismfor shifting the light beams'according to ldifferent Weather conditions, the Verticallyfspread' light beams of the corridor-forming projectors being shi-ftable horizontally and the horizontallyspread light beams of the outer projectors 4being shiftable both vertically and horizontally, -means operable at will to energize thermotors of the corridor-forming projectors, and other means oerable at will to energize the motors ofthe outer projectors.

l5. An approach system `for guiding an aircraft pilot toward a landing runway during landing of the aircraft especially .under adverse weather conditions, comprising va pair of .rows of light projectors arranged :to vform an .aps proach corridor aligned with and leading :to said runway, said projectors 'being adapted'to 'project vertically-spread light beams, and having such spacing and 'such light distribution that a plurality of the projectors of each row Vare'vlsible with substantially equal intensity from any 'point in a vertical plane midway between -said "rows, outer rows of light-projectors parallel to 'the corridor-forming rows on 'theropposite sides vof the corridor and adapted to lead "the `pilot "into said corridor, said outer projectors being 'adapted to project horizontally-spread light .beams which overlap .to forman approach area, the light .pro-

jectors of each outer rowhaving .such .spacing and such vertical distribution -of light-that ,a plurality of said .projectors .are visible .to a .pilot approachingat a certain altitude with substantially equal intensity, all Vof .the .aforementioned light projectors being Adivided into .a ,pluralitylof successive .groups longitudinally of the approach system, ,and .means .for .selectively energizing .the

17 lamps of the light projectors according to said groups.

16. An approach system for guiding an aircraft pilot toward a landing runway during landing of the aircraftl especially under adverse weather conditions, comprising a pair of rows of light projectors arranged to form an approach corridor aligned with and leading to said runway, said projectors being adapted to project vertically-spread light beams, and having such Vspacing and such light distribution that a plurality of the projectors of each row arevisiblev with substantially equal intensity from any point in a vertical plane midway between said rows, outer rows of light projectors parallel to the corridor-forming rows on the opposite sides of the corridor and adapted to lead the pilotinto said corridor, said outer projectors being adapted to project horizontally-spread light beams which overlap to form an approach area, the light projectors of each outer row having such spacing and such vertical distribution of light that a plurality of said projectors are visible to a pilot approaching at a certain altitude with substantially equal intensity, said outer projectors being arranged to provide a plurality of successive groups longitudinally of the approach system, the successive groups decreasing in width toward said runway, and means for selectively energizing the lamps of the light projectors according to said groups.

17. An approach system for guiding an aircraft pilot toward a landing runway during landing of the aircraft especially under adverse weather conditions, comprising al pair of rows of light projectors arranged 'to form an approach corridor aligned with and leading to said runway, said projectors being adapted to project vertically-spread light beams, and having such spacing and such light distribution that a plurality of the projectors of each row are visible with substantially equal intensity from any point in a vertical plane midway between said rows, outer rows of light projectors parallel to the corridor-forming rows on the opposite sides of the corridor and adapted to lead the pilot into said corridor, said outer projectors being adapted to project horizontally-spread light beams which overlap to form an approach area, the light projectors of each outer row having such spacing and such vertical distribution of light that a plurality of said projectors are visible to a pilot approaching at a certain altitude with substantially equal intensity, all of the aforementioned light projectors being divided into a plurality of successive groups longitudinally of the approach system, means for selectively energizing the lamps oi. the light projectors according to said groups, and means for moving the various light projectors so as to shift the light beams according to different weather conditions.

18. An approach system for guiding an aircraft pilot toward a landing runway during landing of the aircraft especially under adverse weather conditions, comprising a pair of rows of light projectors arranged to form an approach corridor aligned with and leading to said runway, said projectors being adapted to project verticallyspread light beams, and having such spacing and such light distribution that a plurality of the projectors of each row are visible with substantially equal intensity from any point in a vertical plane midway between said rows, outer rows of light projectors parallel to the corridor-forming rows on the Opposite sides of the corridor and adapted to lead the pilot into said corridor, said Vouter projectors being adapted to project horizontally-spread light beams which overlap to form an approach area, the light projectors of each outer row having such spacing and such vertical distribution of light that a plurality of said projectors are visible to a pilot approaching at a certain altitude with substantially equal intensity, all of the aforementioned light projectors being divided into a plurality of successive groups longitudinally of the approach system, means for selectively energizing the lamps of the light projectors according to said groups, and means for moving the various light projectors so as to shift the light beams according to different weather conditions.

19. An approach system for guiding an aircraft pilot toward a landing runway during landing of the aircraft especially under adverse weather conditions, comprising a plurality of rows of light projectors arranged to form an approach corridor aligned with and leading to said runway, said projectors being adapted to project vertically-spread light beams, other rows of light projectors parallel to the corridor-forming rows on the opposite sides of the corridor and forming therewith an approach area, said other projectorsbeing adapted to project horizontally-spread light'beams, all of the aforementioned light projectors being divided into a plurality of successive groups longitudinally of the approach system, means for selectively energizing the lamps of the light projectors according to said groups, and means for moving the various light projectors so as to shift said vertically-spread light beams horizontally and to shiftl said horizontallyspread light beams both vertically and horizontally, whereby to adapt the system to different weather conditions. j

20. An approach system for guiding an aircraft pilot toward a landing runway during landing of the aircraft especially under adverse weather conditions, comprising a plurality of rows of light projectors arranged to form an aps DIOach corridor aligned with and leading to said runway, said projectors being adapted to project vertically-spread light beams, other rows of light projectors parallel to the corridor-forming rows on the opposite sides of the corridor and forming therewith an approach area, said other projectors being adapted to project horizontallyspread light beams, and being arranged to provide a plurality of successive groups longitudinally of the approach system, the successive groups decreasing in width toward said runway, means for selectively energizing the lamps of the light projectors according to said groups, and means for moving the various light projectors so as to shift said vertically-spread light beams horizontally and to shift said horizontally-spread light beams both vertically and horizontally, whereby to adapt the system to different weather conditions. C

21. An approach system for guiding an aircraft pilot toward a landing runway during landing of the aircraft especially under adverse weather conditions, comprising a plurality of rows of light projectors arranged to form an approach corridor aligned with and leading to said runway, other rows of light projectors parallel to the corridor-forming rows on the opposite sides of the corridor and forming therewith an approach area, and means for moving the various light projectors so as to shift the light beams of the corridor-forming projectors horizontally and to shift the "light beams of 'the approach-'forming projectors both vertically l:and horizontally, whereby r"to adapt the system-to different :weather conditions.

122. An vapproach system for guiding anaircraft pilot toward a landing runway during *landing of the faircraft' especially under -adverse weatl-ierV conditions, y-corrxpr'i'sing :a pair vof rows yof `=ligiit proj ectorsiarranged 'to 'for-m an approach corridor aligned with' and leading to said runway, said proj'ectorshaving such spacing and ysuch light distribution that a plurality rof projectorsiof-each now are Visible with substantially equal intensity from any point .in V-afvertical plane midway betweenrisaid rows, -and outer rows of light projectorsrparallel to the corridor-formingrows -on the opposite sides of the corridor -and adapted to leadthe pilot-intosaidcorridon said outer pron jectorsihavin'g `such spacing andsuch verticaldistrbn'tion of light that a plurality of .said projeo'torsare yisible to va pilot kapproaching at a' certain altitude with 4substantially equal intensity.

:23. An approach .system for -guiding -anai-rcraft" pilot `toward 'a landing runway during landingof the :aircraft especially under `adverser weather conditions; comprising a pair o'f Vrows of'lig'ht projectors :arranged to'form an approachcorridor align'ed vwith and' leading to said runwayifsa'id projectors havingl such spacingsand such 'light distributi'onrthat a plurality cf fthe projectors o'f each rowfare 'visible with substantially equal intensity from 'any -point in -avertical plane midwayfbe'tween said rows, outer rows of light projectors :parallel to the `corridor-*forming rows on the :opposite sides -o'f vthe corridor and adaptedto lead `the :pilot into 'said corridor, -said outer 'projectors having such spacing'andf'such vertical'distribution of light that a plurality `of said pro-A v' jectors are visible to a pilot approaching 'at a 'certain altitude with substantially equal'intenslity,

means ffor adjusting saidfcorridor-forming lpro-,

ject'ors to adjust their beams according to ground visibility, and means *for yadjusting A'said'.v"outer y projectors to ceiling.

:24. 'an appwachfsystem rrgpiamg'an aircraft tous# their*beansrecording@ j pilot toward a landing runway Vduring landing of the aircraft especially under adverse weather conditions, comprising a pair of rows of light projectors arranged to forman approach corridor aligned with and leading to said runway, said projectors having'such spacing and such light distribution that Ava plurality of the projectors of each row are visiblewith substantially equal tintensity from any point in a vertical Aplane mid'- way between said rows, outer rows'of vlight 'projectors parallel 'to the corridor-formingrows on the opposite 'sides oi :the corridor and adapted to lead'the 'pilot into saidY corridor, vsaid outer projectors having such -spacing 'andYV such Vvertical distribution of light that a plurality oi'said projectors y'are visible to a pilot Yapproaching at a Vcertain altitude with substantially equal intensity, means 'for moving said corridor-forniing proec'tors to adjust Ytheir V'beams accordinjgtov ground visibility, means for Amoving said vouter..

projectors "to vadjust their 'beams 'accordingto ceiling, and 'means for controlling the bright;-

nessof the light beams of all of said projectors.

JOHNB. BARTOW.

REFERENCES cI'rElo The" following references are. oflrecord in the meesters/diarreas.' f

,AY simplified-System fforf'Landing ynunja; litem 

